This invention relates to emergency evacuation equipment for aircraft, in particular, to inflatable aircraft evacuation slides.
The requirement for reliably evacuating airline passengers in the event of an emergency is well known. Emergencies at take-off and landing often demand swift removal of the passengers from the aircraft because of the potential for injuries from fire, explosion, or sinking in water. A conventional method of quickly evacuating a large number of passengers from an aircraft is to provide multiple emergency exits, each of which is equipped with an inflatable evacuation slide. Although evacuation slides permit passengers to quickly and safely descend from the level of the aircraft exit door to the ground, the requirement that each and every aircraft exit door be equipped with an inflatable evacuation slide means that commercial aircraft must devote substantial payload capacity to the carrying of multiple evacuation slides which hopefully will never be used. Accordingly, there has long existed the desire in the industry to make the inflatable evacuation slides as light as possible. One common way of providing an evacuation slide of minimal weight is to design the slide to operate at high pressure. A high pressure inflatable tubular structural member such as those out of which aircraft evacuation slides are constructed, can be made smaller in cross-section, thereby using less weight in fabric, while maintaining the same rigidity as a larger, lower pressure structure. The principal limitation in designers"" ability to utilize high inflation pressures, however, is that the T-joints that are necessary to join the tubular structural members into a composite such as an evacuation slide fail at inflation pressures much lower than that which the remainder of the tubular structural member could withstand. Although the problem of T-joint failure is well known and the desire to utilize higher and higher inflation pressures has long existed, there has not heretofore been a solution to the problem of creating a lightweight T-joint capable of withstanding high inflation pressures compatible with conventional assembly methods for such structures.
The present invention provides a high strength T-joint for inflatable tubular structures in which the opening in the side wall of the first structural member is smaller in cross-section than the second structural member that is joined to it. In one embodiment of the present invention, the T-joint is formed by forming a butt joint between the end of a transverse support member and the side wall of a side rail member of an inflatable evacuation slide. The opening in the side wall of the side rail member is sized to match the end of the transverse support member so that a sealing flange can be applied to the inner surface of the joint to provide an airtight seal. This results in a joint in which the opening is as large as the transverse support member. A reinforcing flange comprising a disk-shaped piece of fabric having a center opening is then bonded to the interior surface of the side rail member over that portion of the sealing flange that is bonded to the side rail member. The opening in the reinforcing flange is substantially smaller than the opening in the side rail member (and, therefore, the cross-sectional area of the transverse support member). Therefore, the reinforcing flange partially blocks the fluid communication between the side rail member and the transverse support member, but substantially reduces the size of the discontinuity in the side wall of side rail member, thereby substantially increasing the circumferential (xe2x80x9choopxe2x80x9d) load capacity of the side wall of the side rail member. By reinforcing the side wall of the side rail member, substantial load is taken off the T-joint thereby substantially increasing the rupture pressure of the joint.